terraform: fix dot output for meta resources

terraform/graph_dot.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/hashicorp/terraform/depgraph"
+	"github.com/hashicorp/terraform/digraph"
 )
 
 // GraphDot returns the dot formatting of a visual representation of
@@ -141,6 +142,49 @@ func graphDotAddResources(buf *bytes.Buffer, g *depgraph.Graph) {
 		buf.WriteString(edgeBuf.String())
 		buf.WriteString("\n")
 	}
+
+	// Handle the meta resources
+	edgeBuf.Reset()
+	for _, n := range g.Nouns {
+		_, ok := n.Meta.(*GraphNodeResourceMeta)
+		if !ok {
+			continue
+		}
+
+		// Determine which edges to add
+		var edges []digraph.Edge
+		if hasDiff {
+			for _, e := range n.Edges() {
+				rn, ok := e.Tail().(*depgraph.Noun).Meta.(*GraphNodeResource)
+				if !ok {
+					continue
+				}
+				if rn.Resource.Diff == nil || rn.Resource.Diff.Empty() {
+					continue
+				}
+				edges = append(edges, e)
+			}
+		} else {
+			edges = n.Edges()
+		}
+
+		// Do not draw if we have no edges
+		if len(edges) == 0 {
+			continue
+		}
+
+		for _, e := range edges {
+			target := e.Tail()
+			edgeBuf.WriteString(fmt.Sprintf(
+				"\t\"%s\" -> \"%s\";\n",
+				n,
+				target))
+		}
+	}
+	if edgeBuf.Len() > 0 {
+		buf.WriteString(edgeBuf.String())
+		buf.WriteString("\n")
+	}
 }
 
 func graphDotAddResourceProviders(buf *bytes.Buffer, g *depgraph.Graph) {